沈阳东北大厦钢结构电梯井装配式施工工艺的应用

建筑工程的产业化已成为建筑行业发展的趋势。基于整体装配式框架结构已经拥有成熟的工程管理经验和成套的施工技术,本文立足现场实际操作要点与细节,形成了一套实用性很强的装配式施工工艺。     

如何有效提高工程管理中的建筑工程造价管理水平

我国建筑行业近年来取得了突飞猛进的发展,与此同时,作为建筑工程管理重点的造价管理水平也急待提高,以便更加适合现代化管理的需要。笔者结合多年的实践经验,分析了工程造价管理中的问题与提高的相应对策,以供读者参考。     

暴雨过后地下车库上浮原因分析及处理

上海某住宅小区地下车库在暴雨过后出现局部上浮,导致框架柱、顶板出现裂缝的现象。针对该突发情况,进行了原因分析,在不影响建设单位使用功能和总体安排的条件下提出了经济、快捷、实用的处理措施,保证了地下车库的安全使用。     

某交行宿舍现浇楼板裂缝的分析

混凝土现浇楼板裂缝影响到房屋的质量和使用要求,必须引起重视并采取措施来进行控制。文章结合实际案例,分析裂缝产生的原因,提出预防措施,并给出处理方法,供设计和施工单位参考。     

镁质波形瓦机械化设备的研制

讲述了镁质波形瓦机械化设备的构造,并对生产过程中碰到的难题作了剖析,也指出了其中的不足之处。     

Kinetic modeling of simultaneous polycondensation and free radical polymerization for polyurethane/poly(methyl methacrylate) interpenetrating polymer network

A comprehensive kinetic Monte Carlo algorithm has been developed to investigate the formation process of a polyurethane/poly(methyl methacrylate) (PU/PMMA) interpenetrating polymer network (IPN), in which a component independent strategy is proposed to perform the simulation of simultaneous polycondensation and free radical polymerization. An empiric diffusion model based on the mass fraction of polymer is used to quantify the effect of diffusional limitations on MMA polymerization. Results show that the presence of acrylic monomers has little impact on the formation rate of PU, but the presence of the PU network can accelerate the polymerization of MMA. In addition, the effects of component mass ratio, acrylic cross-linker concentration, and [NCO]/[OH] ratio on the IPN formation kinetics are investigated based on the kinetic model. It is believed that the as-developed modeling strategy can be extended to other IPN systems and provide a better understanding of the interactions between chemically independent networks.     

爆破致裂技术在立井井筒基岩段工作面注浆中的应用

刘庄煤矿风井井筒累深794m，净直径6．5m。井筒掘进到386．7m深时，揭露厚度18．2m左右的石英砂岩，实测涌水量达到54．95m^3／h，掘砌施工困难。为了保证井筒通过该段岩层施工顺利，进行了工作面预注浆。注浆时采用了孔内爆破致裂技术增大浆液扩散半径，提高注浆效果，达到了预期目的。简要介绍了爆破致裂及注桨施工工艺。     

Sintering Behavior and Dielectric Properties of Ultra‐Low Temperature Fired Silver Molybdate Ceramics

Ag₂MoO₄ ceramic was prepared by using the solid‐state reaction method, which could be sintered at 450°C for 2 h, having a relative permittivity of 8.08, a Qf value of 17 000 GHz, and a temperature coefficient of resonance frequency about ?133 ppm/°C. Ag₂MoO₄ ceramic was chemically compatible with silver but reacted seriously with aluminum to form (Ag_0.5Al_0.5)MoO₄ during the sintering. The fitting of infrared spectra and the Shannon's additive rule were employed to study intrinsic dielectric behaviors of the ceramics at microwave region. Ionic displacive polarization and the electronic polarization contributed almost equally to the dielectric permittivity of the ceramic at microwave region. The Ag₂MoO₄ ceramics could be a good candidate for ultra‐low temperature co‐fired microwave devices.     

Selective hydrogenation of furfural to cyclopentanone over Cu-Ni-Al hydrotalcite-based catalysts

A series of Cu-Ni-Al hydrotalcites derived oxides with a (Cu+Ni)/Al mole ratio of 3 with varied Cu/Ni mole ratio (from 0.017 to 0.5, with a Cu ratio of 0.0125 to 0.25) were prepared by co-precipitation method, then applied to the hydrogenation of furfural in aqueous. Their catalytic performance for liquid phase hydrogenation of furfural to prepare cyclopentanone was described in detail, considering reaction temperature, catalyst composition, reaction time and so on. The yield of cyclopentanone was influenced by the mole ratio of Cu-Ni-Al based heterogeneous catalyst and depended on the reaction conditions. The yield of cyclopentanone was up to 95.8% when the reaction was carried out under 413 K with H₂ pressure of 40 bar for 8 h. The catalysts were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM) and H₂ temperature-programmed reduction (H₂-TPR).     

Tuning of dielectric and ferroelectric properties in single phase BiFeO3 ceramics with controlled Fe/Fe ratio

Single phase multiferroic BiFeO₃ (BFO) ceramics were synthesized with controllable amount of Fe²⁺ and oxygen vacancies in a very wide concentration range. Double ferroelectric hysteresis loops are observed in fresh BFO ceramics at room temperature without any aging processes. Detailed study shows that this is due to the defect dipoles which have preferential orientations antiparallel to the direction of spontaneous polarization, providing a driving force for domain back-switching. The dielectric constant of BFO could be enormously enhanced by 100 times by increasing the Fe²⁺ content, employing a polaronic relaxation process.